Package org.eclipse.persistence.history

Class AsOfClause

java.lang.Object
org.eclipse.persistence.history.AsOfClause
All Implemented Interfaces:
Serializable
Direct Known Subclasses:
AsOfSCNClause
public class AsOfClause extends Object implements Serializable
Purpose:Wraps an immutable value for a past time. A session, query, or expression can be as of a past time.

For Oracle 9R2 Flasback corresponds to the sub clause which appears between the table and alias name in the FROM clause: SELECT ... FROM EMPLOYEE AS OF TIMESTAMP (value) t0, ...

For generic historical schema support, a special criteria can be added to the where clause for each table in a select: ((t0.ROW_START <= value) AND ((t0.END IS NULL) OR (t1.END > value)))

Responsibilities:

  • By default AsOfClause is a timestamp. To specify a system change number use AsOfSCNClause.
  • For Oracle 9R2 Flashback prints the correct AS OF clause before the alias name in the FROM clause.
  • Read-only: the wrapped value can not change.
See Also:
Author:
Stephen McRitchie

  • Field Details

    • NO_CLAUSE

      public static final AsOfClause NO_CLAUSE

  • Constructor Details

    • AsOfClause

      protected AsOfClause()

    • AsOfClause

      public AsOfClause(Date date)

    • AsOfClause

      public AsOfClause(Timestamp timestamp)

    • AsOfClause

      public AsOfClause(Calendar calendar)

    • AsOfClause

      public AsOfClause(long time)

    • AsOfClause

      public AsOfClause(Long time)

    • AsOfClause

      protected AsOfClause(Number number)

    • AsOfClause

      public AsOfClause(Expression expression)

    • AsOfClause

      protected AsOfClause(AsOfClause wrappedValue)

  • Method Details

    • equals

      public boolean equals(Object object)
      INTERNAL: Return if the as of is equal to the other. Equality of asOf clauses is complex (with subclasses), so only use identity.
      Overrides:
      equals in class Object

    • printSQL

      public void printSQL(org.eclipse.persistence.internal.expressions.ExpressionSQLPrinter printer)
      INTERNAL: Prints the as of clause for an expression inside of the FROM clause.

    • getValue

      public Object getValue()
      PUBLIC: The past time represented by the receiver. Either a timestamp, a system change number, or an Expression.

    • isAsOfSCNClause

      public boolean isAsOfSCNClause()
      PUBLIC: Indicates that value is a system change number or an expression evaluating to one.

      In Oracle the value will have to be printed using the syntax AS OF SCN(value) instead of AS OF TIMESTAMP(value).

      See Also:

    • isUniversal

      public boolean isUniversal()
      PUBLIC: Answers if this is a UniversalAsOfClause, one to be applied to the entire selection criteria.

      Used when a query is made as of a past time.

    • toString

      public String toString()
      Overrides:
      toString in class Object